1. Field of the Invention
The present invention relates to an indicating device and more particularly to such an indicating device which indicates data of a camera-to-object distance (hereinafter referred to as an object distance) for flash photography determined on the basis of a film speed, a diaphragm aperture value and amount of light to be emitted from the electronic flash device (hereinafter referred to as emitted light amount). One example of the object distance data is a data of an effective object distance that guarantees a proper exposure with a given amount of flash light. In other words, the effective object distance means the distance for which the proper exposure is guaranteed when a picture is taken of an object at that distance, with the object being illuminated by the given amount of flash light. Another example is an automatic flash available object distance range which means such an object distance in which the proper exposure is guaranteed for an object within the range, with the object being illuminated by automatically controlled flash light. The flash light may be controlled in such a way that the light projected from the flash device and reflected by the object is measured and that the flash light emission is interrupted when the amount of reflected light reaches the predetermined level expected to provide a proper exposure.
2. Description of the Prior Arts
Many cameras have been proposed wherein amount of expoure compensation or adjustment from a predetermined amount of exposure is manually set; thus a picture can be taken with a desired exposure to produce a particular photographic effect intended by the user. When the user makes a flash photograph with such compensated exposure, it is necessary to either adjust the emitted flash light or change the object distance by an amount corresponding the desired exposure compensation amount. The present invention relates to an indicating device for indicating the object distance for flash photography with the distance being changed in accordance with the exposure compensation. The invention is contemplated to eliminate the following inconvenience.
In an electronic flash device wherein the effective object distance of flash photography is indicated through a mechanical or electric calculation device in accordance with manually set values such as the film speed, the diaphragm aperture and emitted light amount, a manual adjustment may be performed on the flash device to change the value of the film speed or the diaphragm aperture by an amount comensurate with the amount of the exposure compensation set on the camera. However, such a design requires manual adjustment of the flash device as well as a camera adjustment for the exposure compensation, resulting in an unnecessarily complex operation. If the user fails to make the adjustments, the resultant picture will not have the photographic effect intended by the user. Also, the camera and the flash device must be readjusted when a flash photograph with a proper exposure is desired after a flash photograph with the compensated exposure has been taken. Another flash device has been proposed wherein data of a set film speed and diaphgram aperture are supplied from a camera to a flash device so that the flash device determines the predetermined amount of exposure on the basis of the supplied data and the data of the maximum flash light amount to be emitted by the flash device, with the determined distance being introduced (see a Japanese laid open patent application with a laid-open No. 59-109034). The proper exposure object distance is such a distance that an object at the distance can be illuminated with sufficient amount of light to effect sufficient exposure for the picture to be taken. However, the proposed flash device is not designed so that the object distance data changes in accordance with the amount of exposure compensation set in the camera. Hence, if the compensation function is required, the flash device must be provided additionally with a manual setting means and calculating means for changing the object distance data in accordance with the set exposure compensation amount, resulting in bulkiness of the flash device. Further, the provision of the manual setting means makes the manual setting operation complex and increases the possibility of failure of achieving the desired photographic effect, as noted in the case above.